Battery element containing metal inhibiting additives

ABSTRACT

A battery element of a lead acid battery including a negative plate, a positive and a separator having a metal inhibiting additive that reduces the detrimental effects of at least one impurity on the negative plate.

RELATED APPLICATIONS

This application is a Continuation application of application Ser. No.08/675,395, filed Jul. 2, 1996. now U.S. Pat. No. 5,759,716, whichpatent is a continuation in part of Ser. No. 8/631,639 filed Apr. 8,1996, now abandoned. This earlier filed application is incorporated inits entirety herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to an improved lead acid battery elementcontaining metal impurity inhibiting polymeric additives which are addedto the positive active material, negative active material and/or batteryseparator to inhibit the detrimental effects of certain metals on theefficiency of a lead acid battery, particularly the negative platebattery element and to macroporous additives that enhance activematerial utilization efficiency and improvement in the utilization ofsulfuric acid electrolyte necessary for the discharge reaction of a leadacid battery.

Metal impurities can be introduced into a lead acid battery through theuse of any of the materials used in the manufacture of the battery. Forexample, metal impurities can be introduced in the lead and leady oxidesused in the manufacture of the active material, the materials ofconstruction including the lead grids, alloying agents, electrolyte andwater. Nearly all metallic impurities, if they are nobler than lead,have a smaller hydrogen overvoltage than pure lead. Therefore, theyincrease hydrogen evolution even if they are deposited in minuteconcentrations on the surface of the negative plates. These metals causea continued gas evolution even after charging is completed. Hydrogen isevolved on the deposited metal with low hydrogen overvoltage, which canbe short-circuited with lead. The effect of metal on the gassingparticularly postcharge gassing decreases in the following sequence: Pt,Au, Te, Ni, Co, Fe, Cu, Sb, Ag, Bi and Sn. The presence of 0.3 ppm ofplatinum in the acid can cause a doubling of the self-discharge rate.Tin can produce this effect at 0.1%. Freshly deposited antimony isespecially active. Besides the discharge of the negative plates withconcomitant hydrogen evolution, these materials also move the end ofcharge voltage of the negative plates toward more positive values. Thehydrogen evolution increases with rising acid density. Because thehydrogen overvoltage decreases with temperature, the self-dischargeincreases.

In addition, antimony is often added to grid lead in order to make thelead more fluid and more easily cast into the shapes necessary forstorage battery grids. Further, it also hardens the resulting casting sothat it can be further processed in the plant without damage. In certainbattery applications, it may be necessary for the battery to withstandextreme resistance to corrosion of positive plate grids. In that event,higher antimony contents typically within the range of 4.5 to 6 percentare incorporated into the grid to form a lead antimony alloy. Antimonyin these concentrations are generally only used in positive gridsparticularly grids intended for corrosion resistant batteries. Corrosionresistance typically means the ability to withstand the destructiveeffects of excessive charge or overcharge.

Antimony in the grid metal produces a definite effect on the chargevoltage characteristics of the fully charged wet battery. The higher theantimony percentage in the grid metal, the lower the charge voltage andconversely, as the antimony is decreased so the charge voltage increasesuntil pure lead is attained, which produces the highest voltage oncharge. Since the use of antimony has gradually been lowered from amaximum of about 12.0% to a maximum of about 6.0% antimony, the chargevoltage of average batteries has increased.

Contaminant metals, hereinafter referred to as metal impuritiesincluding antimony from the positive grids, during service life, slowlygoes into solution in the sulfuric acid electrolyte and from there it isbelieved to electroplate onto the surface of the negative plates. Oncethere, it acts as an additional electrode with the grid and the leadactive material of the negative plates. This combination creates localaction, promoting self-discharge and contributes to poor wet batteryshelf life. In addition, the battery's charge voltage slowly decreasesduring life and, in the voltage regulated electrical circuit of a car,the difference between the two becomes greater. The car voltageregulator is set at a voltage just slightly higher than the normalcharge voltage of the battery. Thus, the generator is able to restoreelectrical energy to the battery, as needed, to keep it charged. Withmetal deposition and the lowering of the battery charge voltage, thegenerator output into the battery increases as an overcharge, whichhastens the deterioration of the battery in service, until failureoccurs. Therefore, it is very desirable to inhibit the detrimentaleffects of antimony on the negative plate.

SUMMARY OF THE INVENTION

A new battery element which inhibits the detrimental effect of solublemetal impurity on the negative plate has been discovered. In brief, thebattery elements include the addition of an organic polymer havingfunctional groups with a preferential affinity for the metal impurity inthe cation or anion state, to the positive active material, the negativeactive material or the separator which separates the positive andnegative plates within a lead acid battery and which typically is areservoir for sulfuric acid electrolyte.

A new battery element which improves utilization efficiency of theactive material in a lead acid battery has been discovered. In brief,the battery elements include the addition of macroporous containingparticle additives to the active material in the positive or negativeplates of a lead acid battery to improve overall utilization efficiencyand the utilization of sulfuric acid electrolyte during discharge of thebattery.

DETAILED DESCRIPTION OF THE INVENTION

In one broad aspect, the present battery elements comprise the additionof an organic polymer containing functional groups with a preferentialaffinity for metal impurity in the cation or anion state to the positiveactive material, the negative active material and/or the separator whichseparates the positive plates from the negative plates in a lead acidbattery. In a preferred embodiment, the organic polymers are porous,i.e. the porosity of the polymer allows the soluble metal impurity inthe electrolyte to contact both the outer surface of the polymers andthe internal surfaces created by the porosity of the organic polymers.The functional groups having a preferential affinity for metal impurityinclude both functional groups on the outer surface and internalsurfaces in contact with soluble metal impurity in the electrolyte. Themetal impurity inhibiting additives are typically incorporated into thenegative active material, the positive active material and/or theseparator in an amount sufficient to inhibit the detrimental effects ofmetal impurity on the negative plate. In another broad aspect, thepresent battery elements comprise the addition of macroporous additivesto the active material present in the positive and/or negative plates ina lead acid battery. In a further preferred embodiment, the macroporousparticles have a reduced affinity for bonding with the active materialin the positive and negative plates.

As set forth above, metal impurities can be introduced into the batteryduring the battery manufacturing process, particularly in the startingmaterials used for battery manufacture. Many of the metal impurities canexist in the anion or cation form i.e. a negative or positive chargerespectively in sulfate solutions such as that represented by sulfuricacid electrolyte. Depending on the molarity of the sulfuric acidelectrolyte and the metal impurity, such cation/anion forms can changeas the molarity changes. Depending on such sulfuric acid molarity, it isbelieved that platinum, gold, thallium, nickel, cobalt, iron, copper,antimony, silver, bismuth and tin can exist as anions even though suchexistence as anions may be weak or unstable. Further, such anion formsmay predominant at the sulfuric acid electrolyte concentrations whichexist after battery charging. One of the particularly detrimental metalimpurities is platinum.

As set forth above, such metal impurities can be introduced into thelead acid battery during manufacturing. In a number of battery designs,grid materials not having antimony as an alloying agent are used forbattery manufacture. However, even in these types of batteries usingnonantimony containing grids, antimony can be introduced as an impurityin the starting materials for battery manufacture including the startinglead and leady oxide type materials.

As set forth above, antimony which is present in the positive grid as analloying agent can be oxidized and/or corroded to form a solubleantimony ion which diffuses and/or migrates to the negative plate.Antimony at the negative plate can produce a number of detrimentalproblems such as self discharge and gassing particularly hydrogenformation. Antimony ion from the positive grid can exist in both theanion and cation form, i.e. a negative or positive charge respectively.It is believed that the form of the anion or cation is dependent on theoxidation state of the antimony, i.e. +3 or +5, the molarity of thesulfuric acid and the battery voltage. For example, it is believed thatantimony can exist as SbO2+ cation and SbO3− anion in the antimony +5state and as SbOSO4−, Sb(SO4)²⁻ SbO2 in the antimony +3 state. These +3anion forms are believed to exist when the molarity of the sulfuric acidis greater than one but may not exist at the fully recharged batteryvoltage. In addition, it is believed that antimony may exist as Sb+3 orSbO+ in the antimony +3 state again depending on molarity and batteryvoltage. As set forth above, the sulfuric acid electrolyte participatesin the discharge reactions taking place in the lead acid battery. Thus,the wt % sulfuric acid can decrease from 30-40 wt % sulfuric acid tofrom 10-14 wt % sulfuric acid depending on the type of battery designand the initial sulfuric acid concentration in the electrolyte. Theamount of sulfuric acid remaining will be dependent on the percent ofdischarge of the battery with less sulfuric acid remaining whenbatteries are discharged to 80% or more.

The organic polymers having functional groups with a preferentialaffinity for metal impurities in the anion or cation state inhibit thedetrimental effects of soluble metal impurity on the negative plate.While the exact mechanism of inhibition is not known, it is believedthat the metal impurity anion or cation is bound by the functional groupsuch as by the anion replacing the anion present on the functional groupin an anionic polymer or by a cation replacing the cation when theorganic polymer contains cation functional groups. Although anion and/orcation replacement is believed to be one mechanism for inhibiting theadverse effects of metal impurity ions, metal impurities can also formcomplexes and/or be solvated to inhibit the detrimental effect of metalimpurities on the negative plate and such mechanisms are included inthen the term inhibiting. One of the major discoveries of the batteryelements of this invention is the inhibition of metal impurities overthe varying sulfuric acid molarities and battery potentials (voltages)that occur during the charge discharge reactions in a lead acid battery.Further it has been discovered that the metal impurity which has beeninhibited by the organic polymer additive is not substantially anddetrimentally desorbed and/or released from the polymer under thesulfuric acid molarity and battery voltage conditions and changes in alead acid battery, that is the metal impurity inhibition continuesduring a plurality of charge/discharge reactions within the battery.

As set forth above, the organic polymers containing functional groupscan introduce cations and/or anions into the battery element whichcations or anions can be displaced by the metal impurity anion and/orcation. Further, the affinity of the organic polymer having such metalimpurity inhibiting functional groups have a stronger binding and/orcomplex formation and/or solvation of metal impurity ions when comparedto any intermediate soluble lead ions such as lead +2 which may beformed during the conversion of solid lead, solid lead peroxide toinsoluble lead sulfate. As is known by those having skill within thelead acid battery art, cations and/or anions which are displaced bymetal impurity cations or anions should not introduce any substantialdetrimental effects on battery performance.

As set forth above, one of the classes of organic polymers hasfunctionality which have affinity for metal impurity in the cation form.The metal impurity cation displaces the cation associated with thefunctional group, Typically, the cation displaced can be hydrogen ionor, for example, sodium ion. The organic polymers having such cationfunctionality can be further classified as strongly acidic cationpolymers or weakly acidic cation polymers. Particularly preferredstrongly acidic cation polymers are those containing sulfonic acidgroups or their sodium salt i.e. sulfonic groups preferably in thehydrogen form. Typical examples of polymers containing the sulfonic acidand/or sulfonate functionality are those derived from polystyrenecrosslinked divinylbenzene, phenol-formaldehyde polymers and other likearomatic containing polymers.

As set forth above the organic polymer can have different functionalgroups such as functional groups containing strongly acidicfunctionality such as sulphonic and phosphonic functionality on the sameorganic polymer. As set forth above, strongly acidic cation polymers arepreferred for inhibiting the effects of metal impurities. A particularlypreferred functionality on the polymer is phosphonic acid and/orphosphonate here in after refered to as phosphonic functionality.Typical examples of such functionality are:

where R is typically hydrogen or sodium ion, preferably hydrogen.

In general the phosphonic functionality can be incorporated into thepolymer matrix by chemical reaction including grafting of suchfunctionality, on for example the aromatic portion of polystyrene and/orphenol-formaldehyde polymers. In addition, the functionality can beincorporated by the copolymerization unsaturated vinylmono or gem ofphosphonic acid or ester monomers with other monomers patricularlystyrene, with still other monomers such as acrylate or acrylovitriletogether with a cross-linking agent such as divinylbenzene. A typicalmonomer used for such copolymerization is vinylidene diphosphonic acidor the ester thereof to produce gem phosphonic functionality. Furtherexamples of such polymers are polymers having a plurality of aminoalkylene, phosphonic acid or phosphonate associated with the organicpolymer.

As set forth above bis-derivatives are also useful includingimino-bis(methylenephosphonic acid). The particularly preferredfunctionality is amino methylelephosphonic acid groups on polystyrenecross-linked with divinylbenzene.

As set forth above, phosphonic functionality can be incorporated intothe polymer by reaction with an existing polymermatrix or bycopolymerization of for example a vinyl phosphonic monomer. A preferedpolymer is one containing polymerized styrene monomer either as a homepolymer or an inter polymer with other polymerized monomeric units. Suchpolymers containg polymerized styrene are generally referred to aspolystyrene polymers.

As set forth above the organic polymer can have different functionalgroups such as functional groups containing strongly acidicfunctionality such as sulphonic and phosphonic functionality on the sameorganic polymer.

The weakly acidic cation polymers in general have carboxylicfunctionality and/or the sodium salt associated with the organicpolymer. Typical examples of such polymers are those derived fromunsaturated carboxylic acids such as acrylic, methacrylic or maleiccrosslinked with another monomer such as divinylbenzene or ethylenedimethacrylate. The preferred organic polymers containing cationfunctionality are the strongly acidic cation polymers having sulfonicacid functionality.

As set forth above, the organic polymer can have functionality having apreferential affinity for soluble metal impurity anions, i.e. the anionassociated with the functionality is displaced by the soluble metalimpurity anion in the electrolyte. The organic polymers having anionfunctionality can have both strongly basic and weakly basic anionfunctionality. Typical examples of strongly basic anion containingfunctionality are those having an ammonium functionality associated withthe organic polymer. As set forth above, the anion associated with thefunctionality, typically sulfate or chloride, is displaced by the metalanion within the electrolyte. Typical ammonium groups associated withthe polymer include trimethyl ammonium ion and dimethylethanol ammoniumion. Other groups include isothiouronium and derivatives thereof.Typical examples of organic polymers are polystyrene crosslinked withdivinylbenzene. The ammonium ion with an appropriate anion can beattached directly to, for example, the aromatic ring of the polystyreneor through, for example, a methylene bridge. Typical examples of weaklybasic polymers having anion functionality are polymers which containtertiary aliphatic or aromatic aliphatic amine functionalities on thepolymer such as polystyrene or a polyunsaturated carboxylic acids. Suchpolymers are typically crosslinked with a crosslinking agent such as thecrosslinking agents referred to above. Further, the polymer basic anionfunctionality can be obtained through aliphatic polyamine condensationreactions to produce the organic polymer. Typically, the weak base anionresins contain primary, secondary and/or tertiary amine groups generallyas a mixture. Typical examples of such amine groups are trimethyl amineand dimethylethanolamine. The preferred organic polymers having aniontype functionality are the strongly basic anion containing functionalityparticularly for their strong binding and low release or desorption ofmetal impurity properties preferably having ammonium functionality,particularly for incorporation into the negative plates. Since theelectrolyte in the lead acid battery is sulfuric acid, it is preferredto use sulfate as the anion to be displaced by metal anion.

As set forth above the organic polymers can contain primary secondary ortertiary amine groups including aliphtaic polyamene functionality.Further as set forth above, such organic polymers can contain aliphaticamine functionality. Further, as set forth above such polymers cancontain amine functionality with acid functionality. Particularlypreferred functionalities associated with the organic polymer whichcontain both amine and acidic functionality are those containingsecondary and tertiary amine functionality and strong acidfunctionality, such as for example, the examples set forth above.

A particularly preferred class of aliphatic aromatic amine functionalityare those having amino pyridine groups associated with the organicpolymer. Examples of such groups can be represented by the formula.

where in R is preferably an aliphatic substituent, an aliphaticpolyamino substituent or a 2-picolene containing substituent R′ ispreferably alkylene, preferably methylene and R″ is a non-substantiallyinterfering substituent, preferably hydrogen.

Particularly preferred additives are organic polymers havingfunctionality from 2-picolylamine, N-methly-2-picolylamine,N-2hydroxyethyl)-2-picolylamine, N-(2-methylaminoethyl)-2-picolylamineand bis-(2-picolyl)amine.

The aromatic aliphatic amine functionalities particularly the2-picolylamine, such as bis-(2-picoly)amine, are particularly useful ininhibiting the detrimental effects of copper and nickel.

As set forth above the organic polymers can contain primary secondary ortertiary amine groups including aliphtaic polyamene functionality.Further as set forth above, such organic polymers can contain aliphaticamine functionality. Further, as set forth above such polymers cancontain amine functionality with acid functionality. Particularlypreferred functionalities associated with the organic polymer whichcontain both amine and acidic functionality are those containingsecondary and tertiary amine functionality and strong acidfunctionality, such as for example, the examples set forth above.

The organic polymers having functional groups with affinity for metalimpurity are typically within the particle size ranges, porosities,surface areas, additive concentration and such other physical propertiesset forth below with respect to porosity additives. The porosity of thepreferred organic polymers can vary over a wide range such as within theranges set forth below with respect to micro and macro porosity. Theporosity of the preferred organic polymers is that which allows themetal impurity ion, cation and/or anion to permeate the organic polymerparticle thereby affording good contact with the functional groupsattached to the external and internal surfaces of the particles. Thetotal displacement capacity of the organic polymer having suchfunctional groups is typically greater than one milliequivalent ofdisplaceable anion or cation per gram of polymer, preferably greaterthan three and still more preferably greater than five.

Any suitable positive active electrode material or combination of suchmaterials useful in lead-acid batteries may be employed in the presentinvention. The positive active electrode material can be prepared byconventional processes. For example, a positive active electrodematerial precursor paste of lead sulfate and litharge (PbO) in water canbe used, or conventional pastes, such as those produced from leadyoxide, sulfuric acid and water, can be used. After the paste is appliedto the grid material, it is dried and cured. The precursor paste may beconverted to lead dioxide by applying a charging potential to the paste.

Any suitable negative active electrode material useful in lead-acidbatteries may be employed in the present invention. One particularlyuseful formed negative active electrode material comprises lead, e.g.,sponge lead. Conventional lead paste prepared from leady oxide, sulfuricacid, water and suitable expanders can be used.

Each of the cells of a lead acid battery further includes anon-electrically conductive separator acting to separate the positiveand negative electrodes of the cell and to hold electrolyte. Anysuitable material may be used as a separator provided that it has nosubstantial detrimental effect on the functioning of the cells orbattery. Typical examples of separator material for batteries includeglass fibre, sintered polyvinyl chloride and microporous polyethylene,which have very small pore sizes. Certain of these separators are formedas envelopes, with the pasted plates inside and the separator edgessealed permanently. Typically only the positive plates are encased inthe separator. Separators uses for sealed lead-acid batteries operatingon the oxygen recombination principle, i.e., oxygen recombinantbatteries include one or more layers of silica-based glass, preferablyseparators formed of a highly absorptive porous mat of acidwettablebinder free microfine glass fibers. Typically, a mix of fibers may beemployed whose individual fibers have an average diameter in the rangeof a bout 0.2 to about 10 microns, more preferably about 0.4 to 5.0microns, with possible minor amounts of larger gauge fibers tofacilitate production of the mat. The porosity is preferably high, morepreferably in the range of about 80% to about 98% and still morepreferably about 85% to about 95%, if in the compressed state in thecell (slightly higher in the uncompressed state). The separatorpreferably has a relatively high surface area, more preferably in therange about 0.1 to about 20 m2/g, which facilitates the absorption andretention of relatively large amounts of acid electrolyte volumetricallywhile, if desired, still having a substantial unfilled pore volumepermeable to oxygen for transport directly through the separator forconsumption at the negative electrode. The particularly preferredseparator materials have a surface area as measured by the BET method ofin the range about 0.2 to about 3.0 m2/g., 30 especially about 1.0 toabout 2.0 m2/g.

As set forth above metal impurities are particularly detrimental insealed lead acid batteries operating on the oxygen recombinationprincipal, i.e. recombinant batteries. A number of impurity metals canexert a deleterious effect on the performance of recombinant batteriesby for example, effecting one of more of the performance requirements ofthe recombinant batteries such as by increasing oxygen, evolution at thepositive electrode, increasing hydrogen evolution at the negativeelectrode, inhibiting oxygen recombination at the negative electrode andin increasing the amount of water lost by the battery. Typical examplesof metals that are particularly deleterious in recombinant batteries arearsenic, antimony, cobalt, chromium, nickel and tellurium.

As set forth above, the metal impurity inhibiting additives can beincorporated directly into the positive active material or negativeactive material for reducing the detrimental effects of the solublemetal impurity on the negative plates. Further, the metal impurityinhibiting additives, as set forth above, can be coated on the separatorsuch as the glass fiber mats used in lead acid batteries. Further, themetal impurity inhibiting additives can be incorporated into the porouspolymeric separators, such as polyvinyl chloride and microporouspolyethylene. Typical concentrations of the additives associated withthe separator is less than about 10 wt % preferably less than about 5 wt% basis the weight of the separators. The preferred metal impurityinhibiting additives are the porous organic polymers which allow for theinhibiting effect of the additives while not detrimentally adverselyeffecting the flow of electrolyte from and/or through the separator tothe positive and negative plates.

In another broad aspect for manufacturing tin dioxide coated poroussubstrates, the process comprises contacting a porous substrate with acomposition comprising a tin oxide precursor, such as tin chlorideforming components, including stannic chloride, stannous chloride, tincomplexes and mixtures thereof, preferably stannous chloride, atconditions, preferably substantially non-deleterious oxidizingconditions, more preferably in a substantially inert environment oratmosphere, effective to form a tin oxide precursor-containing coating,such as a stannous chloride-containing coating, on at least a portion ofthe substrate. The substrate is preferably also contacted with at leastone dopant-forming component, such as at least one fluorine component,at conditions, preferably substantially non-deleterious oxidizingconditions, more preferably in a substantially inert atmosphere,effective to form a dopant-forming component-containing coating, on atleast a portion of the substrate. The coated porous particles areparticularly useful in a number of applications, particularly lead acidbatteries, for example, monopolar and bipolar batteries, catalyst,resistance heating elements, electrostatic dissipation elements,electromagnetic interference shielding elements, electrostatic bleedelements, protective coatings, field dependent fluids and the like. Inpractice the particles which are preferred for use in such applicationsin general have an average length in the range of from about 20 micronsto about 7 mm and an average thickness in the range of from about 20microns to about 7 mm, the average length and thickness being differentor the same depending on particle geometry and application. As set forthabove, the substrate can be optimized for a particular application andthe particular electrical and/or mechanical requirements associated withsuch end use application. For example, in applications in which theparticles are combined with other materials, such as polymers andpositive active material of a lead acid battery and depending on therequirements of the application, ranges of from about 3 microns to about300 microns, or even less than about 5 microns, typically ranges of fromabout 3 microns to about 150 microns or from about 5 microns to about 75microns are useful. The porous inorganic substrates, can becharacterized by bulk density (gm/cc) which is the weight or mass perunit volume considered only for the particle itself, i.e., includes theinternal pore volume, surface area (M2/gm), total pore volume(cc(hg)/gm), pore size distribution and percent apparent porosity. Ingeneral, it is preferred that the bulk density be from about 3% to about85% more preferably from about 10% to about 70%, more preferably, fromabout 10% to about 60% of the true density of the substrate material.Bulk densities less -than about 5% are also useful. In addition, theporous substrate can have a wide range of surface area (M2/gm) of fromabout 0.01 to about 700 preferably having a moderate to high surfacearea, preferably, from about 10 M2/gm to about 600 M2/gm, morepreferably, from about 50 M2/gm to about 500 M2/gm.

The pore volume is preferably from about 0.4 cc/gm to about 3.5 cc/gm,oreven up to about 5 cc/gm, more preferably from about 0.7 cc/gm toabout 4.5 cc/gm more preferably from about 0.7 cc/gm to about 3.25cc/gm. The pore size distribution can vary over a wide range and canhave various distributions including multi-modal, for example,bi-modadistribution of pores including macro pores and micro pores.There ideally exists a relationship between pore diameter, surface areaand pore volume, thus fixing any two variables generally determines thethird. In general, the mean (50%) pore diameter for macro pores, i.e.,generally classified as having a pore diameter greater than about 750angstroms can vary from about 0.075 microns to about 150 30 microns,more preferably, from about 0.075 microns to about 10 microns. Microporosity, generally classified as a porosity having a mean pore diameterof less than about 750 angstroms can vary over a wide range. In general,the mean pore diameter for micro porosity can vary from about 20angstroms to about 750 angstroms, more preferably, from about 70angstroms to about 600 angstroms. The ratio of macro to micro porositycan vary over a wide range and depending on the application, can bevaried to provide optimized performance as more fully set forth underthe various applications. In general, the ratio of percent macroporosity to micro porosity expressed as that percent of the totalporosity can vary from abaut 0% to about 95%, more preferably, fromabout 5% to about 80% macro porosity and from about 100% to about 5%,more preferably from about 95% to about 20% micro porosity.

As set forth above, the porous substrate can be inorganic for example,carbon and carbide, i.e., silicon carbide, sulfonated carbon and/or aninorganic oxide. Typical examples of inorganic oxides which are usefulas substrates include for example, substrates containing one or morealumino silicate, silica, alumina, zirconia, magnesia, boria, phosphate,titania, ceria, thoria and the like, as well as multi-oxide typesupports such as alumina phosphorous oxide, silica alumina, zeolitemodified inorganic oxides, e.g., silica alumina, perovskites, spinels,aluminates, silicates, e.g., zirconium silicate, mixtures thereof andthe like. A particularly unique porous substrate is diatomite, asedimentary rock composed of skeletal remains of single cell aquaticplants called diatoms typically comprising a major amount of silica.Diatoms are unicellular plants of microscopic size. There are manyvarieties that lives in both fresh water and salt water. The diatomextracts amorphous silica from the water building for itself whatamounts to a strong shell with highly symmetrical perforations.Typically the cell walls exhibit lacework patterns of chambers andpartitions, plates and apertures of great variety and complexityoffering a wide selection of shapes. Since the total thickness of thecell wall is in the micron range, it results in an internal structurethat is highly porous on a microscopic scale. Further, the actual solidportion of the substrate occupies only from about 10-30% of the apparentvolume leaving a highly porous material for access to liquid. The meanpore size diameter can vary over a wide range and includes macroporosityof from about 0.075 microns to 10 microns with typical micron sizeranges being from about 0.5 microns to about 5 microns. As set forthabove, the diatomite is generally amorphous and can develop crystallinecharacter during calcination treatment of the diatomite. For purposes ofthis invention, diatomite as produced or after subject to treatment suchas calcination are included within the term diatomite.

As set forth above, porous substrate particles can be in many forms andshapes, especially shapes which are not flat surfaces, i.e., nonline-of-site materials such as pellets, extrudates, beads,includingspheres, flakes, aggregates, rings, saddles, stars and the like. Thepercent apparent porosity, i.e., the volume of open pores expressed as apercentage of the external volume can vary over a wide range and ingeneral, can vary from about 20% to about 92%, more preferably, fromabout 40% to about 90%. In practice, the bead particles, includingspheres, which are preferred for use in certain applications in generalhave a roundness associated with such particles generally greater thanabout 70% still more preferably, greater than about 85% an still morepreferably, greater than about 95%. The bead products of this inventionoffer particular advantages in many of such applications disclosedherein, including enhanced dispersion and rheology.

Acid resistant inorganic substrates, especially fibers, flakes, andglass fibers, are particularly useful substrates, when the substrate isto be used as a component of a battery, such as a lead-acid electricalenergy storage battery.

The porous substrate for use in lead-acid batteries, because ofavailability, cost and performance considerations, generally comprisesacid resistant glass, and/or ceramics more preferably in the form ofparticles, for example, fibers, and/or flakes, and/or beads includingspheres and/or extrudates as noted above.

The solid substrates including organic polymers for use in lead-acidbatteries are acid resistant. That is, the substrate exhibits someresistance to corrosion, erosion, oxidation and/or other forms ofdeterioration and/or degradation at the conditions present, e.g., at ornear the positive plate, negative plate or positive or negative side ofbipolar plates or separator, in a lead-acid battery. Thus, the substrateshould itself have an inherent degree of acid resistance. If thesubstrate is acid resistant, the physical integrity and electricaleffectiveness of the whole present battery element, is better maintainedwith time relative to a substrate having reduced acid resistance. Ifglass or ceramic is used as the substrate particle, it is preferred thatthe glass have an increased acid resistance relative to E-glass.Preferably, the acid resistant glass or ceramic substrate is at least asresistant as is C-or Tglass to the conditions present in a lead-acidbattery. Preferably the glass contains more than about 60% by weight ofsilica and less than about 35% by weight of alumina, and alkali andalkaline earth metal oxides.

As set forth above, one of the preferred applications for use of theporous substrates is in lead acid batteries. Thus, the substrates can beadded directly to the positive active material of a lead acid battery,i.e., the positive electrode to improve battery performance,particularly positive active material utilization efficiency. Oneparticular, unique aspect of the porous substrates is that the substrateis able to provide an internal reservoir for holding sulfuric acidelectrolyte required for carrying out the electro-chemical reactions inthe positive active material. More particularly, the porosity improvesoverall, high rate performance of the positive active material, i.e.improved utilization efficiency at varying rates of discharge time,including high rates and at short discharge times.

As set forth above, the physical properties of the porous substrates canvary widely. It is preferred that the substrate have sufficientmacroporosity and percent apparent porosity to allow for the utilization ofthe electrolyte sulfuric acid contained in the pores during discharge ofthe positive active material and, in addition, that the bulk density beselected to reduce the overall weight of the positive active materialwhile enhancing the overall performance of the battery. In general, thepreferable percent apparent porosity can vary from about 40% to about92%, more preferably, from about 70% to about 90%. The preferred ratioof percent macro porosity to percent micro porosity can vary over a widerange and in general is from about 20% to about 95% macro porosity, morepreferably, from about 45% to about 90% macro porosity with the balancebeing micro porosity. The mean pore diameter, particularly mean macropore diameter, can vary over a wide range with the utilization ofelectrolyte during the condition of the discharge of the battery beingan important factor i.e., at high rate discharges, such as coldcranking, high macro porosity is preferred. Preferred mean macro porediameter is from about 1 micron to about 150 microns, more preferably,from about 5 to about 100 microns or even from about 0.075 micron toabout 10 micron and still more preferably from about 0.1 to about 5microns.

As set forth above, a particularly preferred substrate is a porousparticle, i.e. porous support, particularly beads, including spheres,extrudates, pellets, rings, saddles, stars, etc., preferably within thebulk density, macro porosity, micro porosity, apparent percent porosityand surface areas as set forth above. The coated particles can provideimproved performance in various applications, particularly, in thepositive active material of lead acid batteries. As set forth above, theporous substrate can provide a reservoir for electrolyte sulfuric acidwhich participates in the electrochemical reaction during discharge ofthe positive active material. A particularly unique embodiment of thepresent invention is the use of the porous substrate itself as anadditive in the positive active material to provide a reservoir ofelectrolyte sulfuric acid while providing a light weight additive forincorporation into the positive active material. Such particles areporous and within the ranges as set forth above particularly thepreferred ranges. Such porous substrates can be further coated withadditional components such as with other surface components, which mayimprove recharge, i.e. oxidation as well as other conductive components.As set forth above, the porous substrate with or without an additionalcomponent provides unexpected improvement in the performance of thepositive active material, particularly, in the high rate dischargeconditions such as cold cranking under lower than ambient temperatureconditions.

Another particularly unique embodiment of the present invention is theuse of the porous substrate itself as an additive in the negative activematerial to provide a reservoir of electrolyte sulfuric acid whileproviding a lightweight additive for incorporation into the negativeactive material. Such particles are porous and within the ranges as setforth above for the porous substrates particularly the preferred ranges.Such porous substrates can be further coated with additional componentssuch as other surface components which may improve recharge, dischargeand/or overall life of the battery, such as conductive components whichare stable at the conditions of the negative electrode such as carbonand conductive metals, which coated porous substrates are includedwithin the scope of this invention and the term porous substrate. Theporous substrate with or without an additional component providesunexpected improvement in the performance of the negative activematerial particularly under cold cranking conditions particularlymultiple cold cranking under lower that ambient temperature conditions.As set forth above, the porous substrate can provide unexpectedimprovement in cold 30 cranking typically 0 degrees F or lower during aseries of multiple cold cranking. In addition, the porous substrates inthe negative active material can provide for improved active materialsurface area maintenance and active material morphology maintenanceparticularly at elevated temperatures such as from about 60-80 degrees Cor higher.

Typically, the porous substrates with or without additional componentsare incorporated into the positive and negative active materialtypically at a concentration of up to about 5 wt %, typically up toabout 3 wt % basis the active material.

As set forth above, it is preferred that the porous substrate particleshave sufficient macroporosity and percent apparent porosity for theutilization of the electrolyte sulfuric acid contained in the poresduring discharge of the active material. Further, as set forth above,the preferred mean macropore diameter is from about 0.075 microns toabout 10 microns and still more preferably from about 0.1 to about 5microns. Particularly preferred solid porous particles that exhibitsufficient macroporosity to allow for improved utilization of sulfuricacid electrolyte are silica containing inorganic oxides preferablydiatomites particularly those as set forth above and organic basedmaterials particularly polyolefins still more preferably polypropylene.

As set forth above the porous substrates are acid resistant and includea wide variety of materials, including inorganic and organic basedmaterials. The porous substrates can be in a wide variety of shapes,including shapes that are reduced in size during the manufacture of thepositive active material, such as in the blending and/or mixing of theporous substrate in positive active material manufacture. It ispreferred that the resulting particles if reduced in size maintainporosity parameters within the ranges as set forth above. It is alsopreferred, that the particles have sufficient stiffness and orresistance to detrimental permanent deformation in order to maintainsufficient porosity for the sulfuric acid in the pores to participate ina number of repetitive discharge and charge cycles, such as greater than50 cycles or even 10 cycles.

Further unique embodiment of the present invention is the use of aresilient organic porous substrate which resists detrimental permanentdeformation maintains sufficient porosity for the sulfuric acid in thepores, has resiliency to be deformed under the conditions of dischargeparticularly mechanical forces in the active material of the lead acidbattery and has resiliency to approach or attain its original geometryupon recharge of the battery. In a lead acid battery, the densities ofthe active material change i.e. lead at a density of 11.34 gram/cc, leadperoxide at a density of 9.4 grams/cc, (negative and positive platerespectively) change during discharge of the battery to lead sulfatehaving a density of 6.2 grams/cc i.e. lead sulfate. Upon recharge, thelead sulfate is converted back to lead and lead peroxide in the negativeand positive plates respectively. The resilient organic poroussubstrates have the ability to be deformed during discharge and approachor attain their original geometry during recharge of the battery. Thechanges in density and the ability of the porous substrate to bedeformed allows for increased availability and a greater amount ofsulfuric acid from the pores of the substrate as a function of time toparticipate in a number of repetitive discharge and charge cyclesleading to increased utilization efficiency. Typical examples ofresilient organic porous substrates are elastomeric or rubber-likeporous substrates wherein the pores allow the sulfuric acid toparticipate in discharge and charge cycles. Further examples of suchorganic resilient porous substrates are organic polymers including forexample organic polymers selected from the group consisting ofpolyolefins, polyvinyl polymers, -phenol formaldehyde polymers,polyesters, polyvinylesters, cellulose and mixtures thereof. Thepolymers are selected to be acid resistant and compatible with theactive material at the conditions of the electrode in which they are incontact. Various resilient organic porous substrates particularly porousparticles can be produced using suspension polymerization of a dispersedphase consisting of monomers, cross-linking agents, initiators i.e.catalysts and a co-solvent that functions to aid pore formation. Theparticle size, pore volume, pore size distribution and macroporosity canbe varied within the ranges as set forth above. Such resilient organicporous substrates including particles as set forth above have geometriesand are typically used within the ranges as set forth above for thecoated porous substrates, particularly the preferred ranges and, as setforth above, as to their use in positive active and negative activematerial. Depending on the particular active material in which suchresilient porous substrates are incorporated, such porous substrates canbe further coated with additional components such as with other surfacecomponents which may improve overall properties such as discharge,recharge and life of the active materials.

As set forth above, the porous substrates including resilient poroussubstrates can be incorporated into the positive and negative activematerial. The various porous substrates provide a reservoir ofelectrolyte sulfuric acid in the active material. The reservoir ofsulfuric acid in the porous substrates can be added to the poroussubstrate prior to the addition of the porous substrate to the positiveand negative active material or incorporated into the porous substratefrom the sulfuric acid electrolyte present in the lead acid battery.Further, other liquids such as water can be substituted for sulfuricacid if a liquid is added to the porous substrate prior to the additionof the porous substrate to the active material. As is recognized bythose of skill in the art, only liquids which do not have an adversedetrimental effect on the performance of the battery should be added tothe porous substrate prior to addition to the active material.

In a still further embodiment and as is set forth above, the poroussubstrate particles can be coated with another material. One suchmaterial is a component which gives hydrophobic character to the poroussubstrate, i.e. the porous substrate with the component is not water wetto the same degree as without the component. Such change to hydrophobiccharacter can enhance the flow of electrolyte within the active materialby limiting the bonding of the active material to the pores present inthe porous particles and to particle surfaces. A particularly preferredcomponent is a silica based size having hydrophobic alkyl groups such asmethyl, ethyl or isooctyl which provide for hydrophobic character on thesurface of the porous particles. Many of the organic porous particleswithin the scope of this invention have inherent hydrophobic propertiessuch as the polyolefins whereas other have a combination of hydrophilicand hydrophobic properties. As set forth above, it is preferred that theporous particles have sufficient hydrophobic character to reduce thepermanent bonding of the active material to the surfaces of the porousparticles particularly the pores of the particles. The reduced bondingof the active material to the porous particles allows for improveddiffusion of the sulfuric acid electrolyte to the interior of the activematerial associated with the positive and/or negative plate.

As set forth above, the additives are typically incorporated into thepositive and negative active material at a concentration of up to about5 wt %. The porous particle additives and the antimony inhibitingadditives are incorporated during battery manufacture preferably duringthe production of the paste prior to application on the grid material.The additives can be incorporated into, for example, the lead, leadyoxide powders to which the sulfuric acid and water are added.Alternatively, the additives can be mixed into the precursor paste priorto applying on the grid material. It is preferred that the additives beincorporated such as to provide a uniform distribution of the additiveparticles throughout the entire paste, active material.

Further, the porous substrate as set forth above can be an acidresistant organic material, including organic polymeric materials as setforth above. Preferred polymers are polyolefin polymers, polyvinylpolymers, phenolformaldehyde polymers, polyesters, polyvinylesters andmixtures thereof. Preferred polymers are polyolefins, preferablypolypropylene, phenolformaldehyde polymers and polyvinylester,particularly modacrylic polymers.

EXAMPLE 1

A negative plate battery element is manufactured from a commercialbattery paste having a density of 4.3 gm/cc. An organic polystyrenepolymer prepared from styrene as at least one monomer and cross-linkedwith divinylbenzene having both strong acid and secondary aminofunctional groups is incorporated into a freshly prepared wet paste at aconcentration of 1.5 wt %, basis the lead content of the paste prior toincorporation of the additive. The additive is combined with its weightof 5 ut % sulfuric acid to fill the pores of the additive prior tomanufacturing the paste. The additive is distributed in the pasteuniformly and pasted on a series of negative grids containing noantimony. The negative plates are cured and assembled into a 12-voltbattery with 6% antimony grid positive plates, formed and tested. Traceamounts of nickel is also present in the lead. The detrimental effect ofantimony and nickel on the negative plate is inhibited.

EXAMPLE 2

A negative plate battery element is manufactured from a commercialbattery paste having a density of 4.3 gm/cc. An organic polymer preparedfrom the copolymerization of styrene and cross-linked withdivinylbenzene having different acid functional groups with at least onebeing sulfonic is incorporated into a freshly prepared wet paste at aconcentration of 1.5 wt %, basis the lead content of the paste prior toincorporation of the additive. The additive was combined with the sameweight of 5 ut % sulferic acid to fill the pores of the additive priorto manufacturing the paste. The additive is distributed in the pasteuniformly and pasted on a series of negative grids containing noantimony. The negative plates are cured and assembled into a 12-voltbattery with 6% antimony grid positive plates, formed and tested. Traceamounts of nickel is also present in the lead. The detrimental effect ofantimony and nickel on the negative plate is inhibited.

While this invention has been described with respect to various specificexamples and embodiments, it is to be understood that the invention isnot limited thereto and that it can be variously practiced within thescope of the following claims.

What is claimed is:
 1. A battery element useful as at least a portion ofa plate in a lead acid battery comprising active material, sulfuric acidelectrolyte including metal impurity ion and an acid resistant metalimpurity inhibiting amount of one or more porous organic polymers havinga plurality of chemically different functional groups which one or morepolymers have a preferential affinity over lead ion for at least oneelectrolyte soluble metal impurity ion more nobler than lead at thedischarge/charge electrochemical conditions of the positive and negativeplates provided that at least a portion of said one or more organicpolymers are incorporated into said active material and in contact withthe metal impurity ion containing electrolyte to allow said ion topermeate the porous polymer.
 2. The element of claim 1 wherein one ofthe organic polymers has strong acid functional groups.
 3. The elementof claim 1 wherein one of the organic polymers has aliphatic aminefunctional groups.
 4. The element of claim 1 wherein one of the organicpolymers has aliphatic amine and strong acid functional groups.
 5. Theelement of claim 3 wherein the aliphatic amine functional groups areselected from the group consisting of secondary amines, tertiary amineand mixtures thereof.
 6. The element of claim 4 wherein the aliphaticamine functional groups are selected from the group consisting ofsecondary amines, tertiary amine and mixtures thereof.
 7. The element ofclaim 2 wherein one of the organic polymers is cross-linked polystyreneand the cross-linking is by divinylbenzene.
 8. The element of claim 4wherein one of the organic polymers is cross-linked polystyrene and thecross-linking is by divinylbenzene.
 9. The element of claim 5 whereinone of the organic polymers is cross-linked polystyrene and thecross-linking is by divinylbenzene.
 10. The element of claim 6 whereinone of the organic polymers is cross-linked polystyrene and thecross-linking is by divinylbenzene.
 11. The element of claim 2 whereinthe soluble metal impurity is selected from the group consisting ofantimony, cobalt and nickel.
 12. The element of claim 4 wherein thesoluble metal impurity is selected from the group consisting ofantimony, cobalt and nickel.
 13. The element of claim 10 wherein thesoluble metal impurity is selected from the group consisting ofantimony, cobalt and nickel.
 14. A battery element useful as at least aportion of the negative plate in a lead acid battery comprising negativeactive material, sulfuric acid electrolyte including metal impurity ionand an acid resistant metal impurity inhibiting amount of one or moreporous organic polymers having a plurality of chemically differentfunctional groups which one or more polymers have a preferentialaffinity over lead ion for at least one electrolyte soluble metalimpurity ion more nobler than lead at the discharge/chargeelectrochemical conditions of the positive and negative plates providedthat at least a portion of said one or more organic polymers areincorporated into said active material and in contact with the metalimpurity ion containing electrolyte to allow said ion to permeate theporous polymer.
 15. The element of claim 14 wherein one of the organicpolymers has strong acid functional groups.
 16. The element of claim 14wherein one of the organic polymers has aliphatic amine functionalgroups.
 17. The element of claim 14 wherein one of the organic polymershas aliphatic amine and strong acid functional groups.
 18. The elementof claim 16 wherein the aliphatic amine functional groups are selectedfrom the group consisting of secondary amines tertiary amines andmixtures thereof.
 19. The element of claim 16 wherein one of organicpolymers is a cross-linked polystyrene and the cross-linking is bydivinylbenzene.
 20. The element of claim 17 wherein one of the organicpolymers is cross-linked polystyrene and the cross-linking is bydivinylbenzene.
 21. The element of claim 18 wherein one of the organicpolymers is cross-linked polystyrene and the cross-linking is bydivinylbenzene.
 22. The element of claim 20 wherein a second polymer ispresent which has strong acid functional groups.
 23. A battery elementuseful as at least a portion of the negative plate in a lead acidbattery comprising negative active material, sulfuric acid electrolyteincluding antimony ion and an acid resistant antimony inhibiting amountof one or more porous organic polymers having a plurality of chemicallydifferent functional groups which one or more polymers have apreferential affinity over lead ion for antimony ion thedischarge/charge electrochemical conditions of the positive and negativeplates provided that at least a portion of said one or more organicpolymers are incorporated into said active material and in contact withthe antimony ion containing electrolyte to allow said ion to permeatethe porous polymer.
 24. The element of claim 23 wherein one of theorganic polymers has strong acid functional groups.
 25. The element ofclaim 23 wherein one of the organic polymers has aliphatic aminefunctional groups.
 26. The element of claim 23 wherein one of theorganic polymers has aliphatic amine and strong acid functional groups.27. The element of claim 23 wherein one of the organic polymer iscross-linked polystyrene and the cross-linking is by divinylbenzene. 28.The element of claim 26 wherein one of the organic polymers iscross-linked polystyrene and the cross-linking is by divinylbenzene.